To minimize head injuries such as skull fractures and head and scalp lacerations in athletic events, it is well known, indeed mandatory in most instances, to wear specially designed headgear. Typical protective headgear used in football contests is comprised of rigid shell internally lined with a plurality of energy-absorbing pads. One type of lining which has shown promise uses a bladder, typically disposed between the helmet and padding that contacts the wearer's head. An example of a helmet protecting system using such a bladder is found in U.S. Pat. No. 3,600,714 issued to Cade on Aug. 24, 1971 in which the bladder is formed with a centrally disposed sump and valve connected to front, rear, and side extensions. The bladder has a multiplicity of connecting cells and is filled with a hydraulic liquids such as various types of oils or glycerine. Upon impact, the incompressible fluid in the cells is distributed to the other cells and sump. Thus, the effect of the force at the point of impact is dissipated through out the bladder system. Still another advantage to this type of bladder is that it can be adjusted to a limited extent to accommodate various head sizes by changing the size of the cells through an increase or decrease in the amount of fluid placed in the cells.
More recently, gaseous inflatable liners have been used within helmets to assist in dissipating impact forces. However, the structure of the prior art gaseous inflatable liners dictate that the liners be molded into complex shapes. Such shapes are formed into a substantially rigid liner that complement the top part of the wearer's head prior to inflation and before being placed within the shell of the helmet. Because of the complex shape of the liner, it is necessary to use sophisticated and more costly molding techniques such as "rotational" molding. This process is a three stage, no pressure plastic molding process. In the first stage, a mold containing a plastic charge is heated and then rotated bi-axially. Heat transfer causes the charge to melt within the mold. During the second stage, the mold continues to rotate but is cooled. During this stage the plastic charge coats the internal surfaces of the mold and hardens. The formed hollow piece is then removed from the mold during the third stage and the mold then is recharged.
Prior art liners also suffered from problems of non-uniform inflation wherein some portions of the liner may be over-inflated whereas others are under-inflated. Non-uniform inflation can adversely affect the fit of the helmet and the protection it provides. In prior art helmets, it is especially common for the portion of the liner adjacent the inflating valve to over-inflation and bulge out.
It is therefore an object of the present invention to provide for an inflatable liner having a final shape and structure that is easily manufactured by a plurality of different molding techniques and adapted to be easily flexed and positioned into a shell of a helmet.
It is still another object of the present invention to provide an inflatable liner that when inserted into a helmet frame minimizes non-uniform inflation.
It is yet another object of the present invention to provide for an inflatable liner that is essentially flat on the side adapted to abut the helmet and essentially rounded on the other side adapted to abut the wearer's head.
Still another important object of the present invention is to provide an inflatable liner that can be removably inserted into and positioned among a configuration of pads so as to form a co-extensive surface with the surfaces of the pads for abutment against the head of the wearer.
These and other objects and advantages of the present invention will become apparent upon a reading of the following description along with the appended drawings.